1. Field of the Invention
The invention relates to a driving force transmission apparatus and a vehicle equipped with a driving force transmission apparatus.
2. Description of Related Art
In an existing art, there is known a driving force transmission apparatus for a vehicle, which includes an outer rotating member, an inner rotating member that is located coaxially with the outer rotating member and that is rotatable relative to the outer rotating member, a clutch that is formed of outer clutch plates spline-fitted to the outer rotating member and inner clutch plates spline-fitted to the inner rotating member, and a cam mechanism that presses the clutch (see, for example, Japanese Patent No. 4192955).
In the driving force transmission apparatus described in Japanese Patent No. 4192955, in order to suppress abnormal noise that occurs when differential rotation between the outer rotating member and the inner rotating member is reversed, a first spline gap (L1) between a second cam member of the cam mechanism that presses the clutch and the inner rotating member is set smaller than a second spline gap (L2) between the inner clutch plates and the inner rotating member. With the thus configured driving force transmission apparatus, a residual amount of cam thrust is reduced immediately before the inner clutch plates and the outer clutch plates respectively contact tooth flanks of spline teeth of the inner rotating member and outer rotating member on the opposite side in the circumferential direction due to reversal of differential rotation. As a result, generation of abnormal noise is suppressed.
However, in the driving force transmission apparatus described in Japanese Patent No. 4192955, in order to set the first spline gap (L1) smaller than the second spline gap (L2), it is necessary to set the circumferential width of each protrusion of the inner clutch plates spline-fitted to the inner rotating member to a value smaller than at least the circumferential width of each protrusion of the second cam member. Therefore, it is difficult to ensure the load bearing of the inner clutch plates, and the torque transmission capacity of the clutch may be limited.